Rail holddown assembly



Feb. 10, 1970 D. D. BROWN 3, 9

RAIL HOLDDOWN ASSEMBLY Filed Feb.-25. 1968 I I I gjmmk 3 27 MI 25 27 2amva/vroe.

aauawr 0. BROWN 9W, QLLIM ifiziriig Lga United States Patent O 3,494,558RAIL HOLDDOWN ASSEMBLY Delmont D. Brown, North Baltimore, Ohio, assignorto The D. S. Brown Company, North Baltimore, Ohio, a corporation of OhioFiled Feb. 23, 1968, Ser. No. 707,500 Int. Cl. E01b 9/44 U.S. Cl.238-349 6 Claims ABSTRACT OF THE DISCLOSURE Rail holddown systemembodying holddown assembly with resiliently biased holddown memberspressing against upper face of base flange of railroad rail; resilientbias preferably is compressed elastomer body positioned between holddownmember and upper leg of loop strap fitted around base plate and seatedin groove therein.

BACKGROUND OF THE INVENTION The present invention concerns holddownsystems particularly adapted to securely position a railroad rail on asupport member or underlying structure. The invention particularlyconcerns the holddown systems adapted for use with concrete ties,concrete beds, metal superstructures, and like rail support structures.It further pertains to other uses wherein one member is to be held inposition relative to another member and may be used in lieu of boltconnections, welded connections, etc.

Railroad rails traditionally have been mounted on wooden cross tiesspaced at close intervals by the driving of railroad spikes into theties with the head portion of the spike overlapping the base flange ofthe rail. This has been true of below ground, and on ground rail systemsand above ground, or elevated, rail systems. With the fairly recentadvent of improvements in the structural strength of concrete, railsystems embodying concrete ties or concrete beds have awakened theinterest of railroad designers. Concrete beds or ties requireconsiderably less maintenance and have a longer useful life than do thetraditional wooden ties.

The adaptation of rail systems to the use of concrete ties and concreteroad beds, however, also require a departure from the traditionalconcept of holding the rail on the ties, i.e., by spikes being driveninto the wooden ties. Holddown systems for rails on concrete ties and/orconcrete road beds or metal superstructures have been developed inrecent years. Known holddown systems embody heavy metal structures. Someutilize metal components in torsion stress as the force-exertingmembers. A specific object of the present invention concernsimprovements in rail holddown systems wherein the traditional, woodentie concept is abandoned in favor of prestressed concrete ties, metalsuperstructures and/ or concrete road beds in below ground, on ground orelevated rail systems.

BRIEF SUMMARY OF THE INVENTION Briefly, the invention concerns holdingsystems in general, i.e., systems for holding one member relative toanother comprising a first member, a second member contiguous thereto tobe held in fixed position relative to said first member, and means fortransmitting thrust between said members including a compressivelydeformed bias member, preferably a solid elastomer body having oppositesubstantially parallel faces exerting an outward elastic recovery thrustagainst substantially parallel faces with lines of thrust forces in saidcompressively deformed members being essentially at right angles to saidfaces. An exemplary use thereof comprises rail holddown systems whereinthe railroad rails are secured by a series of holddown devicesmaterially different from and considerably improved over the traditionalrailroad spike. A base member of such device may be fixedly securedrelative to a concrete bed or tie or to other structural systemssupporting the rail, such as metal superstructures in the case ofelevated rail systems. This base member may be a base plate bolted orotherwise attached to the road bed, concrete tie or superstructure. Thesystem further embodies a holddown member comprising a holddown orpressure plate pressed downwardly against the upper face of the baseflange. The pressure exerted thereby is of a relatively high magnitude,i.e., in the order of at least several hundred p.s.i. and a total forceof at least two thousand pounds. This pressure is provided by aresilient bias member, preferably elastomer pressure body, positionedbetween a fixed inverted U- member and the holddown member. Theelastomer body is distorted compressively from its normal, unstressedstate whereby the elastic recovery thrust forces resulting from thecompressive distortion exerts a pressure thrust force of relatively highmagnitude, sufficient to secure the rail tightly on ties or other railsupport members.

The elastomer pressure member is inserted in the holddown system on theconstruction site. As is well known, it is difficult to insert anelastomer member in a highly compressed state. To facilitate suchinsertion, the elastomer member may be compressively distorted orflattened, whereafter its temperature is lowered sufficiently toimmobilize or freeze the member in the compressed or flattened statewhen the compression force is removed. It is maintained at thistemperature until it is inserted on the job in the holddown system. Uponthawing or warming, the elastomer body regains its elastic recoveryproperty and recovers toward its normal shape, which is the shape of theelastomer member before compressive distortion and low temperatureimmobilization thereof. The holddown system is dimensioned so that theinserted elastomer member cannot recover fully its original or normalshape, whereby the elastomer member is in a partially compressed statewhen it exerts its thrust force against the holddown member. Thereby,there exists in effect the elastomer member in a partially compressedstate. Through the utilization of the elastic recovery force of saidmember in attempting to return it to its original or normal state, itfunctions as th pressure exertin body in the holddown system.

The elastomer member may also be compressed between opposing, preferablysubstantially parallel faces of a holddown system or the like by othermeans. For example, the elastomer member may be inserted in anuncompressed state, and one or more shims may be driven between the bodyand the contiguous face of the holddown member to compress the elastomermember. Alternatively, the holddown device may be made in separate partsand assembled on the job site in a manner whereby the elastomer memberis compressed upon assembly. In rail holddown systems, the holddownunits may be mounted on the rail without the elastomer member, which isinserted later.

RELATED APPLICATIONS This invention concerns improvements in holddownsystems of the type disclosed in the pending application of FrankKenneth Hall, filed of about even date herewith. The improvements insaid Hall application reside in holddown structures embodying a baseplate, preferably extending transversely beneath the railroad rail. Thebase plate has provided thereon a holddown unit comprising an invertedU-member having a substantially flat cross leg extending transverselyacross and above the base (substantially parallel with the rail). Theinverted U- member is adjacent the base flange of the railroad rail andthere are preferably two, opposed, holddown units on each base plate onopposite sides at the base flange. The holddown member has an innerportion resting against the upper face of the base flange of the railand extends from said base flange outwardly through the invertedU-member. A resilient bias member, preferably a solid elastomer body,under compressive distortion, is provided between the aforesaid crossleg and the holddown member. The elastic recovery of the resilient biasmember presses the flange-contacting portion of the holddown memberdownwardly against the upper face of the base flange to give a securemounting of the railroad rail on the aforesaid base plate, which is inturn securely mounted by bolts or the like on concrete railroad ties,concrete rail beds, metal superstructures, or the like.

IMPROVEMENTS HEREIN My improvements in the aforesaid Hall holddownsystems reside primarily in the utilization of a loop strap, preferablyof substantially rectangular configuration, as a member for mounting thecompressively distorted, resilient bias member in the rail holddownunit. The loop strap is dimensioned to slip over the end of the baseplate, and the lower cross leg thereof is seated in a transverse groovein the undersurface of the base plate. The upper leg preferably has asubstantially flat, lower face opposing the upper face of the railholddown member, e.g., a substantially flat plate. The compressivelydistorted, resilient bias member exerts its resilient (elastic) recoverythrust between the preferably substantially flat lower face of the uppercross leg of the loop strap and the preferably substantially parallelupper face of the holddown member and thereby press the latterdownwardly against the upper face of the rail base flange.

DESCRIPTION OF THE DRAWINGS A preferred form of the invention isillustrated in the drawing wherein:

FIGURE 1 is an end elevation of an embodiment of a I rail holddownsystem with the railroad rail shown in cross section and the underlyingconcrete tie shown in fragment; FIGURE 2 is a top plan view thereof withthe rail and tie shown in fragment; and

FIGURE 3 is a side elevation thereof with the rail and tie shown infragment.

DESCRIPTION OF THE PREFERRED EMBODIMENT The illustrated embodimentconstitutes a rail holddown assembly wherein the assembly is attached,e.g., by bolts, to a rail supporting structure, which may be a series ofrailroad cross ties, an elevated, ground level or below ground railroadbed, or steel structural members of an elevated monorail or dual railsystem. The ties or railroad bed may be of any suitable material, butgenerally will be concrete. The rail has the usual base flange 11, theupper surface 12 of which generally slopes outwardly but may be at rightangles to the vertical axis of the rail if desired. In the illustratedembodiment the rail holddown system is mounted on the upper face of aconcrete tie 13. Each concrete cross tie has secured to its upper face arail holddown unit 15. The unit 15 comprises a base plate 16 mounted onthe tie by bolts 17 and nuts 18 tightened against bearing or washerplates 19 having a stepped lower segment 20 seated in the rectangularapertures 14 in the outer portions of the base plate 16. The bolts 17are fixedly embedded in the tie 13.

The base plate 16 has on opposite sides of rail 10 two transversedeformations 21 and 22, which form respectively transverse, shallowgrooves 23 and 24 in the underside of base plate 16. These groovesreceive the lower, cross-legs 25 of rectangular loop straps 26, whichare dimensioned to slip over the ends of base plate 16 prior to boltingof the latter to the tie 13.

The loop straps 26 comprise the lower, cross leg 25, side legs 27, andtransversely sloped top cross leg 28. The loop straps 26 are seated ingrooves 23 and 24 in an orientation whereby the lower faces of top crosslegs 28 are substantially parallel to opposing, upper faces of holddownmembers 29.

A rail holddown member 29, e.g., a substantially flat plate, extends atan angular slope corresponding substantially to the respective slopes ofupper surfaces 12 of base flange 11 through each loop strap. The underface 30 of plates 29 thereby substantially flatly rests on respectiveupper surfaces 12. The under face 30 is pressed tightly against theupper surface 12 by a compressively distorted, resilient bias member 31,which comprises in the illustrated embodiment a compressively distorted,solid elastomer body or block. There is a cross bar 32 extendingtransversely of the base plate 16 contiguous to the outer edges of eachholddown member 29. The function of the cross bars 32 is to provide aseat or retainer against which the outer edge 33 of the substantiallyflat pressure plate 29 rests for proper positioning thereof, and also toprevent the latter from working outwardly. If desired, an elastomer pad34 may be provided beneath the base flange 11 and underlying centerportion of base plate 16.

The preferred pressure exerting members comprise an elastomer block orbody which is compressively distorted in the assembly of the rail withthe holddown devices. Prior to inserting them, these blocks or bodiesare distorted by compression into a flattened form, with a dimensionslightlydess than the spaces between cross legs 28 and holddown members29. They are inserted in the distorted or compressed shape andthereafter allowed to recover via the elastic forces of the elastomerblock or body toward its normal state, i.e., the shape it would assumewithout any compressive forces exerted thereon. In this elasticrecovery, the elastomer bodies press against these holddown members andthus exert a downward thrust thereon. This force is in turn transmittedagainst the upper face 12 of the base flange 11 to hold the railsecurely in position.

The opposing faces of the cross legs 28 and respective holddown members29 are preferably substantially parallel, planar faces for achievingmaximum effect of the thrust forces of the resilient bias members 3 1.The latter, in turn, are generally rectangular parallelepipeds in therelaxed (undistorted) state having a height or thickness considerablygreater than the distance between said opposing faces.

As aforesaid, it normally would be diflicult to insert the compressivelydistorted, elastomer bodies between said faces. To facilitate suchinsertion, it is preferred that the elastomer bodies be compressivelydistorted in a flattened shape and frozen or immobilized in this state.They are held at the freezing or low temperature immobilization untilinserted. As the elastomer bodies warm, their resilient properties arerestored and they seek'to resume their shape prior to compressivedistortion and freezing. In so doing, they become wedged between saidfaces and thus exert a downward thrust on the holddown members.

The terms freezing and thawing above, are nontechnical descriptions. Inpractice, the elastomer bodies are formulated so that the elastomercomposition will rigidify through loss of elastic properties, atrelatively low temperatures, i.e., in the order of -40 F. and below. Theelastomers also should have good resistance to atmospheric deteriorationin the presence of sunlight, atmospheric oxygen, and ozone, and shouldretain their elastic properties also at relatively high temperatures onthe order of to F. The elastomer compositions useful for this purposemay be formulated from elastomers which crystallize at relatively lowtemperatures with the loss of elastic properties upon crystallization.Exemplary thereof are low crystallization neoprene elastomers. However,elastomers which are usually considered to be noncrystalline elastomers,e.g., natural rubber and most synthetic rubbers, can be immobilized orrigidified in the compressively distorted state at low temperatures inthe order of F. to 100 F. or even lower. The invention hereincontemplates use of any natural or synthetic rubber composition whereinsuch low temperature immobilization can be attained. The selection of aparticular elastomer composition will depend in part on the climate ofthe locale where the installation is made. In northern parts of thetemperate zone, a low temperature immobilization of 30 F. or below isrecommended. In the arctic zone, a low temperature immobilization of 60F. or below is recommended, whereas in southern parts of the temperatezone and in the tropical zone 0 F. or below would be suitable. In eachinstance, the low temperature immobilization is selected so that it willnot be reached and preferably not even closely approached under thecoldest climate conditions of the particular locale.

The system embodies substantially parallel, opposed faces against whichthe compressively distorted elastomer body is positioned with itsopposite faces pressing against said opposed faces to give an elasticrecovery thrust force urging said faces apart along lines of thrustforce at right angles to said faces. This combination utilizes theelastic recovery forces in the compressed elastomer body moreeffectively than would be the case if the elastomer body were subject totwisting. In the latter case, the torque elastic recovery forces in thetwisted elastomer adopt a sine curve-like configuration. Such recoveryforces are considerably less effective in terms of amount of elasticrecovery thrust forces per unit of distortion or deformation of theelastomer body as compared against the thrust force orientation achievedby this invention.

It is thought that the invention and its numerous attendant advantageswill be fully understood from the foregoing description, and it isobvious that numerous changes may be made in the form, construction andarrangement of the several parts without departing from the spirit orscope of the invention, or sacrificing any of its attendant advantages,the forms herein disclosed being preferred embodiments for the purposeof illustraling the invention.

The invention is hereby claimed as follows:

1. In a rail holddown system embodying, a railroad rail having a baseflange extending along the base thereof supported on members of a railbed, the improvement comprising a rail holddown unit embodying a baseplate, a loop-strap around said base plate adjacent said flange, saidloop-strap having an upper cross leg extending transversely across andabove said base plate, and a lower cross leg beneath said plate, aholddown member extending through said loop-strap with an inner portionthereof resting against the upper face of said flange, and a resilientbias member under compressive distortion between said upper cross legand said holddown member and pressing said inner portion against saidupper face.

2. The improvement as claimed in claim 1 wherein said bias member is abody of solid elastomer.

3. The improvement as claimed in claim 1 wherein said loop-strap is asubstantially rectangular loop dimensioned to slip over an end of saidbase plate.

4. The improvement as claimed in claim 3 wherein said base plate has atransverse groove in the under face thereof, and the lower cross leg ofsaid loop strap is seated in said groove.

5. The improvement as claimed in claim 4 wherein said holddown membercomprises a substantially flat, cross plate extending throughloop-strap, said bias member being compressively distorted between saidupper cross leg and cross plate and pressing said cross platedownwardly, and the inner portion of the underface of said cross platelying substantially flatly against said flange.

6. The improvement as claimed in claim 5 wherein said bias member is abody of solid elastomer.

References Cited UNITED STATES PATENTS 2,008,940 7/1935 Armstrong238-304 2,215,104 9/1940 Kimmel 23 8-304 2,724,558 11/1955 Jones 238-349 ARTHUR L. LA POINT, Primary Examiner R. A. BERTSCH, AssistantExaminer US. Cl. X.R. 238283, 304, 310

